<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        <input type="text" v-model="username">
        <input type="text" :value="username" @input='handle'>
    </div>
    <script src="./node_modules/vue/dist/vue.js"></script>
    <script>
        let vm = new Vue({
            el:'#app',
            data() {
                return {
                    username:''
                }
            },
            methods: {
                handle(event) {
                    this.username = event.target.value;
                }
            },
        })
    </script>
</body>
</html>